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Three Questions on Plant Intelligence

Javier Yanes: There is currently a wide scientific corpus on plants’ cognition-communication-decision making etc., but how should we call all this? Neurobiology? Intelligence? What is the point of the terminological debate from a philosophical perspective?

Michael Marder: When we slot the capacities of plants into a coherent conceptual framework, how we refer to these capacities is not a matter of mere nominalism, that is, of attaching an extraneous label to a phenomenon, which remains unaffected by the name it bears. We touch, rather, upon the very meaning of intelligence, not only tied to the central nervous system but also inherent to life itself. The point is to begin regarding human intelligence as an example, or a subspecies, of the general concept of intelligence, alongside that of plants, animals, and even unicellular organisms. Broadly, intelligence would then designate a set of interactions and a way of negotiating a dynamic, open-ended fit between a living being and its milieu, wherein this being is capable of orienting itself, intending desirable outcomes and avoiding the undesirable ones, making decisions, solving problems, etc. Some of the notable features of plant intelligence are that it is 1) de-centered (or dispersed), 2) modular (akin to “parallel processing”) and 3) directed toward the other thanks to the maximization of exposure to solar radiation. What do these characteristics tell us about intelligence “in general”? Plenty of work is yet to be done to address this question.

Do you believe that there is some reluctance to close this debate because our views about intelligence are too “cerebrocentric”?

Indeed. Many people, including those in the academic world, seem to be unable to differentiate between the physical or physiological structures of biological intelligence and the functions served by these structures. It is not the case that only primates have been successful from the evolutionary point of view. If anything, plants have had much more time to perfect their evolutionary strategies than animals, and in each case the goals have been analogous: to attain the resources necessary for survival, to reproduce, and to occupy a comfortable niche in the environmental milieu. When it comes to the issue of sensitivity, we know, for instance, that plants register a wider range of light waves than we, humans, do. However, plants do not have anything recognizable as eyes. It does not follow from this “lack” that they do not see; on the contrary, they have specialized photosensitive cells, dedicated to capturing different kinds of light. The same is true for intelligence. If plants “lack” the brain, this does not mean that they are incapable of performing the operations we tend to associate with thinking. What exactly enables the functioning of intelligent responses in plants is still a subject of intense debate among scientists: hormonal networks, calcium / potassium absorption mechanisms, neuronal-like networks in the roots? That said, we would be committing an unforgivable fallacy were we to deem plants unintelligent only because we are still ignorant of the specific physiological structures that perform this vital function, without which life (and survival) would have been simply impossible.

In what sense do you think that this knowledge should shape our ethics? Authors like Simcha Lev-Yadun have warned that this could give rise to new extremisms (he uses “salad is murder” as a joke), but there are also initiatives like the reference of the Swiss constitution to “plants’ dignity.” How should we adapt to this new reality?

I firmly believe that, as we learn more about the wonderful capacities of plants, we are obliged to revise the way we treat them. Rather than plant ethics, I think that what is extremist is the refusal to adjust our ethical precepts to the ontological view of plants, currently undergoing a rapid change as a result of new scientific findings. We cannot remain entrenched in the old paradigm of plants as barely alive, passive, machine-like… But neither can we extend a liberal-individualistic ethics to them. The difficult task at hand is finding an ethical and political mode of treating plants that would do justice to their particular mode of existence. I have already mentioned that plant intelligence is dispersed, modular, and oriented to the other. The dividing lines between “individual” and “community” are very loose in the vegetal world: any single plant may be considered a multiplicity of growths symbiotically bound together, while a whole ecosystem, such as a forest in which trees of the same species share their roots, may be viewed as an individual being. As I see it, the ethics of plant life will be one that both respects and engages with multiplicity, taking care not to destroy communities of plants nor to convert them wholesale into the means for satisfying our own needs, producing them for no other purpose than human consumption. We should, instead, work with the plants themselves, making use, if necessary, of their modular parts, of the many aspects of vegetal life that are not “essential” and that can be gifted to us by plants without undue harm to their communal being.

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4 thoughts on “Three Questions on Plant Intelligence”

I just stumbled upon this via Twitter, and am thrilled to read this discussion. To see these ideas discussed is very heartening to me, as I have always had a sense of plants as sentient beings. Fascinating to hear of the Swiss constitution referring to “plant dignity.”
I’ll be looking to read Mr. Marder’s work now. Great interview!

What varies between plants themselves, more so between plants and animals, including humans, is what can count as an individual. All gardeners worry about species of plants, and about maintaining species; but individual variation as it is active among animals surely loops back to make the individual more precious to others than in the sphere of plants, in that it represents possibilities for the future in a more than purely numeric random way?